A surface coating is sometimes applied to a recording medium in order to improve its printing properties. For example, the coating can improve the appearance, ink absorption, and/or image smear resistance of the medium.
Surface coatings can be classified into two general categories—glossy coatings and non-glossy (matte or dull) coatings. Glossy coatings are often desirable, as they are very smooth, and can impart a superior feel and a photograph-like quality to a recorded image.
A coating composition comprising a pigment such as a hydrated aluminosilicate (such as a kaolin clay), titanium dioxide, alumina, silica, or calcium carbonate can be used to make a glossy coating if the composition is applied by cast coating, wherein the composition is dried while contacting a polished metal cylinder or drum (e.g., a polished chromium drum). A glossy pigment coating prepared in this manner is advantageous not only for its gloss, but because the pigment can impart a relatively high rate and capacity of ink absorption to the coating as well. However, the cast coating procedure is relatively slow and costly.
It is possible to make glossy pigment coatings using application methods which are cheaper and faster than cast coating (e.g., bar coating, air-knife coating, roll coating, etc., sometimes followed by calendering), but the overall gloss of the resulting coating is often diminished compared to cast coating. Moreover, glossy pigment coatings prepared using these rapid, inexpensive methods also can be quite brittle, and the coatings often crack and flake upon drying.
Coating compositions comprising resins such as polyolefin resin, polyester resin, polyamide resin, or polycarbonate resin can be applied using the aforementioned rapid, inexpensive coating methods (e.g., bar coating, air-knife coating, roll coating, etc.), to form coatings having a high gloss. However, a recording medium having such a glossy resin coating generally has significantly decreased rates of ink absorption and ink drying compared to a recording medium having a pigment coating.
A need exists for a recording medium having a coating that can be applied using a rapid, inexpensive coating procedure, wherein the coating is non-brittle, and wherein ink applied to the recording medium is rapidly absorbed, and rapidly dries. A need also exists for a coating composition that can be used in preparing such a recording medium, and for a dispersion that can be used to prepare such a coating composition. The invention provides such a recording medium, coating composition, and dispersion.